Step 1

Gather all the ingredients. Preheat oven to 400ºF (200ºC). For a convection oven, reduce cooking temperature by 25ºF (15ºC). Place 1 sheet of pastry on a baking sheet that has been lined with parchment paper. Put another pastry sheet on a different sheet of parchment paper. Defrost for 10 minutes at room temperature.

Step 2

Cut the pastry sheets in half with a scissor. Now you have 4 rectangular sheets. Then make several slits on 2 sheets that will go on top of the pie.

Step 3

Peel the sweet potato and cut it in half lengthwise. Then cut into smaller chunks so they will cook faster.

Step 4

In a pot, put sweet potato and cover it with water. Bring it to a boil and cook until a skewer goes through the potatoes smoothly, about 12-15 minutes. Drain water completely and transfer to a large bowl.

Step 5

Use a potato masher or fork to mash the sweet potato. Add sugar and butter and keep mixing.

Step 6

Add egg yolk and heavy whipping cream and mix well.

Step 7

Now you put the sweet potato mixture on the bottom sheets. Keep about half inch space around the rim. Then cover with the top sheet.

Step 8

Use a fork to pinch the edges.

Step 9

Beat the egg in a small bowl and brush the top of the pastry so it will turn nice golden brown. Sprinkle black sesame seeds on top.

Step 10

Bake for 20-25 minutes, or until golden brown. Let cool a bit and ready to serve in 10 minutes.

Step 11

You can freeze the baked and cooled pies. Wrap them in aluminum foil and put them in a freezer bag. To serve, reheat the pie at 350ºF (180ºC) for 10-15 minutes, until crisp and flaky.